Cleavage reactions Periodates can cleave carbon–carbon bonds on a variety of 1,2-difunctionalised alkanes. The most common example of this is
diol cleavage, which was also the first to be discovered (
Malaprade reaction). In addition to
diols, periodates can cleave
1,2-hydroxy ketones,
1,2-diketones,
α-keto acids,
α-hydroxy acids,
amino acids,
1,2-amino alcohols, and
1,2-diamines, to give aldehydes, ketones, and carboxylic acids. In the presence of strong acid catalyst, like H2SO4 or HNO3
epoxides are also converted into aldehyde or ketones or dicarbonyl compounds. Alkenes can also be oxidised and cleaved in the
Lemieux–Johnson oxidation. This uses a catalytic loading of
osmium tetroxide which is regenerated in situ by the periodate. The overall process is equivalent to that of
ozonolysis. Cleavage reactions proceed via a cyclic intermediate called a periodate ester. The formation of this may be affected by pH and temperature but is most strongly affected by the geometry of the substrate, with
cis-diols reacting significantly faster than
trans-diols. The reactions are exothermic and are typically performed at 0 °C. As periodate salts are only readily soluble in water reactions are generally performed in aqueous media. Where solubility is an issue periodic acid may be used, as this is soluble in alcohols;
phase transfer catalysts are also effective in
biphasic reaction mixtures. In extreme cases the periodate may be exchanged for
lead tetraacetate which reacts in a similar manner and is soluble in organic solvents (
Criegee oxidation). Periodate cleavage is often utilized in molecular biochemistry for the purposes of modifying
saccharide rings, as many five- and six-membered sugars have vicinal
diols. Historically it was also used to determine the structure of monosaccharides. Periodate cleavage may be performed on an industrial scale to form
dialdehyde starch which has uses in
paper production.
Oxidation reactions Periodates are powerful
oxidising agents. They can oxidise
catechol to
1,2-benzoquinone and
hydroquinone to
1,4-benzoquinone.
Sulfides can be effectively oxidised to
sulfoxides. Periodates are sufficiently powerful to generate other strong inorganic oxidisers such as
permanganate,
osmium tetroxide and
ruthenium tetroxide.
Niche uses Periodates are highly selective etchants for certain
ruthenium-based oxides. Several
staining agents use in
microscopy are based around periodate (e.g.
periodic acid–Schiff stain and
Jones' stain). Periodates have also been used as oxidising agents for use in
pyrotechnics. In 2013 the
US Army announced that it would replace the environmentally harmful chemicals
barium nitrate and
potassium perchlorate with
sodium metaperiodate for use in their tracer ammunition. ==Other oxyanions==